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From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Concatenation and Characters
Date: Wed, 23 Oct 2002 11:34:35 +0200
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Date: 2002-10-23T11:34:35+02:00
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On Wed, 23 Oct 2002 09:08:24 +0000 (UTC), Lutz Donnerhacke
<lutz@iks-jena.de> wrote:

>* Dmitry A Kazakov wrote:
>>>However, you can write this:
>>>
>>>    return (1..0 => 123);
>>>
>>>if the component type is Integer, say.  This is annoying, because you
>>>have to invent a completely junk value -- 123 is never used.
>> 
>> BTW, do you know a solution of this problem for generics? Let the
>> array element is a generic parameter and there is no Null_Element
>> parameter, where to get a junk value?
>
>There are several other cases where a default value can't be specified (task).
>Then I use
>   declare
>      empty : Array_Type (Offset_Type'Last ..
>                          Offset_Type'Pred(Offset_Type'Last));
>   begin
>      return empty;
>   end;

There is a pathological case when this does not work:

type Index is new Integer range Integer'First..Integer'First;
type Array_Type is array (Index range <>) of Integer;
   
Empty : Array_Type (Index'Last..Index'Pred (Index'Last));
               -- Constraint_Error

-------------------------------

Could we inroduce an attribute, say S'Empty, which for an array type
would give an empty array and for a discrete type an empty range?

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de